PB Blaster is a penetrating oil/lube that breaks down surface rust on bolts/nuts other components and helps free up rusted threads, dont use it on plastic or rubber because it will eat it away. Im sure everyone here has used at least once and owning a jeep, having a can of it nearby is almost always needed. Heres what it looks like.

 

haha... what is a pb blaster... haha... so yea, poss a bad pulley? check, w/o belt on, that eac pulley spins smooth.